Economic comparison between two challenging approaches for On-Bottom Stability Assessment of Subsea Pipelines

Abstract

Dn-bottom stability design is a critical objective to achieve safe subsea pipelines where such substantial loads may destabilize the pipe, leading to lateral movement. The pipeline's instability causes cracks to form, resulting in the loss of pipe product and pollution of the maritime environment. The purpose of on-bottom stability design is to ensure that the pipe does not go with the flow, becomes laterally unstable in place, and inadvertently interfaces with nearby objects. However, movement is permitted up to specified ranges during the design to enhance stability and optimize the cost of stabilization. The most extensively used and industry-accepted methods for achieving on-bottom stability are AGA/PRCI and DNV-RP-F109, which provide detailed design procedures. The AGA approach is used to conduct a comparison study between its results and those of DNV to determine which is more economically advantageous. Therefore, this research aims to identify which of these two methods is more conservative, preferable by delivering better economic outcomes for an existing 10-inch pipeline placed on sandy soil in the shallow water of 11-m depth. Results show that AGA offers 40 mm of concrete thickness, which is cost-wisely better than DNV that gives a concrete thickness of 120 mm.